Post-tension concrete leave out splicing system and method

ABSTRACT

Devices, systems, and methods for constructing post-tensioned concrete slabs in a new floor construction that has a reduced gap distance between the slabs. The devices, systems, and methods can improve project construction time by reducing the time delay in accessing the floor underneath the slabs due to safety and/or weather conditions.

FIELD

This description relates generally to floor construction usingpost-tensioned concrete slabs.

BACKGROUND

Generally, a process for new floor construction using post-tensionedconcrete slabs requires a gap (also known as a leave out, a pour stripout, etc.) that separates adjacent concrete slabs (also known as poursor castings). Generally, the gap is four feet and more in length. Thatis, several feet in distance separates the two ends of thepost-tensioned concrete slabs. Sometimes the gap distance (the distancewhich separates the two ends of the post-tensioned concrete slabs) maybe called a “width,” but for clarity and consistency, the term “width”is used herein to describe the distance along the direction labeled “W,”and the term “length” is used herein to describe the distance along thedirection labeled “L” (e.g., see FIGS. 1-3). Accordingly, ΔL is usedherein to describe a change in distance along the “L” axis direction.Generally, the gap is filled in (i.e., lap spliced) with a pour strip ata later time, connecting the slabs together to form the entire floor.

Prestressed concrete is a type of reinforced concrete which has beensubjected to external compressive forces prior to the application ofload. Prestressed concrete is categorized as either pre-tensioned orpost-tensioned.

Pre-tensioned concrete is formed by a process including initialstressing of a wire strand system and then casting concrete around thestressed wire strand system. The stress from the wire strand systemtransfers to the concrete after the concrete has reached a specifiedstrength (e.g., cured to a set specification).

Post-tensioned concrete is formed by a process of casting wet concretearound an unstressed wire strand system and then stressing the wirestrand system after the concrete has reached specified strength (e.g.,cured to a set specification). For example, post-tensioned concrete canhave a wire strand system which has a wire enclosed in a duct (e.g.,pipe, conduit, etc.). Concrete is formed around the duct and theconcrete sets and cures. Then, the wire is stressed and grout material(e.g., a mixture of cement, sand, aggregate, and water) is pumped intothe cavity surrounding the wire. The grout material bonds the wire tothe duct, and the duct is bonded to the cured concrete. Thus, the stressapplied to the wire can be transferred to the concrete. The appliedstress (e.g., forces applied to the wire strand system) in thepost-tensioning process causes a volume change (and/or a length change)to the concrete material. The volume change of the concrete materialcauses a change in the length of the concrete slab. The length change isa shortening in the direction parallel to applied stress (e.g., thepost-tensioning force).

FIGS. 1-2 show schematic diagrams of a floor construction 10 accordingto a generally known process using post-tensioned concrete. FIG. 1 showsa top-down plan view of the floor construction 10. The floorconstruction 10 includes post tensioned slabs 12, 14 separated by a gap16. FIG. 1 shows the “width” direction indicated by “W” and the “length”direction indicated by “L” (FIGS. 2 and 3 also show the length directionindicated by “L”). FIG. 2 shows a side view of the floor construction10, also showing the slabs 12, 14, and the gap 16. The floorconstruction 10 is made by a process wherein the post tensioned slabs12, 14 are each poured separately, tensioned independent of each otherafter they have sufficiently cured. Thus, the rebars in thepost-tensioned slab 12 do not necessarily lineup (e.g., axially) withthe rebars in the post-tensioned slab 14.

Each of the slabs 12, 14 changes volume due to their tensioningprocesses. The typical tensioning process for a typical floorconstruction uses the gap 16, which is typically four to eight feet inlength, for accommodating appropriate tooling and equipment (and alsofor access by workers) to tension the slabs 12, 14. Further, the gap 16(i.e., the separation between the two slabs 12, 14) becomes longer(e.g., along direction L shown in FIG. 1) during and after thetensioning of one or both of the slabs 12, 14. That is, the volumechanges in the slabs 12, 14 and the slabs 12, 14 become shorter. Andbecause the slabs 12, 14 become shorter, the separation between them,which is the gap 16, becomes longer.

For example, in a typical hotel floor construction, the gap 16 can beabout sixty to seventy feet in width and four to eight feet in length.Generally, the gap 16 is left open for twenty to thirty days to allowmost of the volume changes (i.e., slab shortening) to occur to thepost-tensioned concrete slabs 12, 14. After the twenty to thirty days,the gap 16 is filled in (i.e., lap spliced) with a pour strip 18 toprovide a structural continuity of the floor construction 10 required bythe final design to resist all required loads.

FIG. 3 shows a close-up schematic view of a portion 20 of the floorconstruction 10 shown in FIG. 2. The portion 20 shows the first slab 12having a post-tensioning wire strand system 22 for stressing theconcrete 23. The slab 12 includes a steel reinforcing bar 24 (also knownas rebar) which reinforces the concrete 23 in the slab 12. Generally,the rebar 24 and other rebar in the slab 12 are somewhat regularlypositioned in the slab 12, and extend out from the end of the slab 12towards the gap 16. The second slab 14, which is also shown in theportion 20, has its own post-tensioning wire strand system 26 forstressing the concrete 27. The slab 14 includes a rebar 28 whichreinforces the concrete 27 in the slab 14. Generally, the rebar 28 andother rebar in the slab 14 are somewhat regularly positioned in the slab14, and extend out from the end of the slab 14 towards the gap 16. Inthe prior art process of forming the floor construction 10, thepositioning of the rebar 28 is not based on or with respect to theposition of the rebar 24. Further, prior to the filling in of the gap 16with the pour strip 18, the rebar 24 extending out from the slab 12 isnot connected to the rebar 28 extending out from the slab 14. That is,prior to the filling in of the gap 16 with the pour strip 18, the rebar24 extending out from the slab 12 is not directly connected to the rebar28 extending out from the slab 14. That is, prior to the filling in ofthe gap 16 with the pour strip 18, the rebar 24 extending out from theslab 12 is not indirectly connected to the rebar 28 extending out fromthe slab 14. Other rebar (s) 30 is (are) positioned, or laid down,inside the gap 16 along the width direction, so that the other rebar(s)30 is (are) perpendicular to the length direction of the rebar 24 and/or28. Then, the pour strip 18 is formed around the rebar 24, 28, 30filling in the gap 16.

Referring back to FIG. 1, in a multi-level building construction havingone or more floors, the floor construction 10 can be placed aboveanother floor. These floors are connected to and accessible via aconstruction elevator 30. Generally, there is only one (or very few)construction elevator 30 that is used during the construction of thebuilding. Accordingly, during the construction of the floor construction10, the slab 12 area can be accessed via the elevator 30. However, theslab 14 area cannot be accessed easily when a gap 16 four feet and moreexists between the slabs 12, 14. That is, construction equipment cannoteasily be moved to slab 14 from slab 12. Thus, generally, theconstruction process requiring access to slab 14 waits the twenty tothirty days until the pour strip 18 is poured to splice the slabs 12, 14together. Further, the gap 16 allows significant weather conditions tointrude into the floor beneath the floor construction 10. Such weatherconditions can also prevent work from being performed in the floorunderneath the floor construction 10. Despite these disadvantages ofhaving long gaps in post-tension concrete construction, waiting and timedelay are generally an accepted part of the-process in the field ofconstruction.

BRIEF SUMMARY

Devices, systems, and methods for connecting post-tensioned concreteslabs in new floor construction reduce the distance (e.g., length) ofthe gap between the post-tensioned concrete slabs as compared toconventional construction. Accordingly, the devices, systems, andmethods disclosed herein advantageously reduce project construction timeby reducing the time delay in accessing the floor underneath the slabsdue to, for example, safety and/or weather conditions.

An embodiment of this concrete construction includes a firstpost-tensioned concrete slab, a second post-tensioned concrete slab, anda cavity-forming device. The first post-tensioned concrete slab and thesecond post-tensioned concrete slab have respective upper surfaces thatare generally aligned. The first post-tensioned concrete slab includes aplurality of first rebars installed therein. The second post-tensionedconcrete slab includes a plurality of second rebars installed therein.The first post-tensioned concrete slab and second post-tensionedconcrete slab are separated by a gap so that the concrete material ofthe first post-tensioned concrete slab is not in contact with theconcrete material of the second post-tensioned concrete slab. Thecavity-forming device forms a cavity. The cavity-forming device isinstalled in the first post-tensioned concrete slab, wherein the cavitycontains a portion of one of the second rebars.

In an embodiment of the concrete construction, the cavity-forming devicehas an end which is connected to an end portion of one of the firstrebars, wherein the end has a threaded surface which mates with athreaded surface of the end portion of the one of the first rebars.

In an embodiment of the concrete construction, a portion of one of thefirst rebars is also contained in the cavity.

In an embodiment of the concrete construction, the cavity-forming devicehas a pair of tubes extending upwardly through the first post-tensionedconcrete slab and providing air access from above the post-tensionedconcrete slab to the cavity, the cavity being filled through one of thetubes with a binding material which fixes the one of the second rebarsin the cavity.

In an embodiment of the concrete construction, the cavity-forming devicehas a pair of tubes extending upwardly through the first post-tensionedconcrete slab and providing air access from above the post-tensionedconcrete slab to the cavity, the cavity being filled through one of thetubes with a binding material which connects together the one of thefirst rebars and the one of the second rebars so that the portion of theone of the first rebars and the portion of the one of the second rebarsare substantially parallel with each other.

In an embodiment of the concrete construction, the cavity-fomiing devicehas a pair of tubes extending upwardly through the first post-tensionedconcrete slab and providing air access from above the post-tensionedconcrete slab to the cavity, the cavity being filled with a bindingmaterial which connects together the one of the first rebars and the oneof the second rebars so that the portion of the one of the first rebarsand the portion of the one of the second rebars are substantiallyinline.

An embodiment of the concrete construction further comprises a secondcavity formed by a second cavity-forming device installed in the secondpost-tensioned concrete slab, wherein the second cavity contains aportion of another of the plurality of the first rebars.

In an embodiment of the concrete construction, the gap has a longerdimension for one side-to-side and a shorter dimension for anotherside-to-side, the shorter dimension being three feet or less.

In an embodiment of the concrete construction, the gap has a longerdimension for one side-to-side and a shorter dimension for anotherside-to-side, the shorter dimension being twelve (12) inches or less. Insome embodiments, the distance of the shorter dimension is from two tosix inches. In some embodiments, the distance of the shorter dimensionis from two to seven inches. In some embodiments, the distance of theshorter dimension is from two to eight inches. In some embodiments, thedistance of the shorter dimension is from two to nine inches. In someembodiments, the distance of the shorter dimension is from two to teninches. In some embodiments, the distance of the shorter dimension isfrom two to eleven inches. In some embodiments, the distance of theshorter dimension is from two to twelve inches.

An embodiment of the concrete construction further comprises a strip ofnon-shrink material being in the gap, wherein the strip has acompressive strength that is greater than or equal to the compressivestrength of the concrete material of the first and second post-tensionedconcrete slabs.

An embodiment of a concrete construction includes a first post-tensionedconcrete slab, a second post-tensioned concrete slab, and acavity-forming device, the first post-tensioned concrete slab and thesecond post-tensioned concrete slab having respective upper surfacesthat are generally aligned, the first post-tensioned concrete slabincluding a plurality of first rebars installed therein, the secondpost-tensioned concrete slab including a plurality of second rebarsinstalled therein, the first post-tensioned concrete slab and secondpost-tensioned concrete slab being separated by a gap so that theconcrete material of the first post-tensioned concrete slab is not incontact with the concrete material of the second post-tensioned concreteslab, the cavity-forming device forming a cavity which together with thedevice form a volume, the cavity-forming device being installed in thefirst post-tensioned concrete slab, wherein one of the second rebarsconnects with the volume, the cavity being filled with a bindingmaterial which connects together the first post-tensioned concrete slaband the one of the second rebars, the gap having a longer dimension forone side-to-side and a shorter dimension for another side-to-side, theshorter dimension being twelve (12) inches or less, the gap being filledwith a strip of non-shrink material, wherein the strip has a compressivestrength that is greater than or equal to the compressive strength ofthe concrete material of the first and second post-tensioned concreteslabs.

In an embodiment of a method for making a concrete constructionincluding a first post-tensioned concrete slab and a secondpost-tensioned concrete slab separated by a gap, the method includes thesteps of forming the first post-tensioned concrete slab with a pluralityof first rebars, wherein the first post-tensioned concrete slab includesa cavity-forming device with a cavity having an opening towards an endof the first post-tensioned concrete slab; prior to pouring a secondconcrete slab, positioning one of a plurality of second rebars for thesecond concrete slab so that a portion of the one of the plurality ofsecond rebars is inside the cavity; pouring the second concrete slab;forming the second post-tensioned concrete slab by tensioning the secondconcrete slab, thus forming the gap between the first post-tensionedconcrete slab and the second post-tensioned concrete slab, wherein thegap has a longer dimension for one side-to-side and a shorter dimensionfor another side-to-side; and after forming the second post-tensionedconcrete slab, securely fixing the portion of the one of the pluralityof the second rebars in the cavity.

An embodiment of the method, the step of securely fixing the portion ofthe second rebar in the cavity includes also securely fixing a portionof the first rebar in the cavity. In an embodiment of the method, theshorter dimension is three feet or less in length.

An embodiment of the method further comprises the step of forming astrip of material in the gap with a non-shrink material, wherein thestrip has a compressive strength that is greater than or equal to thecompressive strength of the concrete material of the first and secondpost-tensioned concrete slabs.

In an embodiment of a method for making a concrete constructionincluding a first post-tensioned concrete slab and a secondpost-tensioned concrete slab separated by a gap, the method comprisesthe steps of forming the first post-tensioned concrete slab, wherein thefirst post-tensioned concrete slab includes a first rebar installedtherein, and an end portion of the first rebar extends into a space thatwill become the gap; before a second post-tensioned concrete slab hasbeen formed, positioning a cavity-forming device having a cavity at anend portion of the first rebar so that the end portion of the firstrebar is inside the cavity, but not securely connecting thecavity-forming device to the end portion of the first rebar; pouring thesecond concrete slab; forming a second post-tensioned concrete slab bytensioning the second concrete slab, thus forming the gap between thefirst post-tensioned concrete slab and the second post-tensionedconcrete slab, wherein the gap has a longer dimension for oneside-to-side and a shorter dimension for another side-to-side; and afterforming the second post-tensioned concrete slab, securely fixing the endportion of the first rebar in the cavity.

An embodiment of the method includes, prior to forming the secondpost-tensioned concrete slab, positioning a second rebar inside thecavity but not securely connecting the cavity-forming device to thesecond rebar; and in the securely fixing the portion of the first rebarin the cavity step, also securely fixing a portion of a second rebar ofthe second post-tensioned concrete slab in the cavity.

An embodiment of the method further includes the step of forming a stripof material in the gap with a non-shrink material, wherein the strip hasa compressive strength that is greater than or equal to the compressivestrength of the concrete material of the first and second post-tensionedconcrete slabs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-2 show plan and elevation schematic diagrams, respectively, of afloor construction according to a generally known process usingpost-tensioned concrete.

FIG. 3 shows an enlarged, elevational schematic view of a portion of thefloor construction shown in FIG. 2.

FIGS. 4-5 show plan and elevation schematic diagrams, respectively, of afloor construction according to an embodiment of the present invention.

FIG. 6 shows a schematic side view of a floor construction according toan embodiment of the present invention.

FIG. 7 shows a schematic side view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 8 shows a schematic side view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 9 shows a schematic side view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 10 shows a schematic side view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 11 shows a schematic perspective view of the floor constructionshown in FIG. 10.

FIG. 12 shows a flow chart of an embodiment of a process forconstructing the floor construction with reduced gap design.

FIGS. 13-18 show schematic side views of floor constructions beingconstructed according to an embodiment of the process.

FIG. 19 shows a schematic side view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 20 shows a schematic side view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 21 shows a schematic side view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 22 shows a schematic side view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 23 shows a schematic side view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 24 shows a schematic plan view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 25 shows a schematic plan view of an embodiment of a floorconstruction according to an embodiment of the present invention.

FIG. 26 shows a schematic plan view of an embodiment of a floorconstruction according to an embodiment of the present invention.

DETAILED DESCRIPTION

The present disclosure may be further understood with reference to thefollowing description and the appended drawings, wherein like elementsare referred to with the same reference numerals. The systems, devices,and methods disclosed herein are directed towards reducing the gapbetween post-tensioned concrete slabs in a floor construction, so thattime delay caused by the existence of conventional gaps in the floorconstruction can be reduced and/or eliminated.

FIGS. 4-5 show schematic diagrams of a floor construction 100 accordingto an embodiment. FIG. 4 shows the “width” direction indicated by “W”and the “length” direction indicated by “L” (FIGS. 5-11 and 13-26 alsoshow the length direction indicated by “L”). The floor construction 100includes post-tensioned concrete slabs 102, 104. FIG. 4 shows a top-downplan view of the floor construction 100. The floor construction 100includes post tensioned slabs 102, 104 separated by a gap 106. FIG. 5shows a side view of the floor construction 100, also showing the slabs102, 104, and the gap 106. The distance of the gap 106 is substantiallyless than the conventional gap. For example, it is possible that the gap106 is less than three feet in distance. In a preferred embodiment, thegap 106 is a foot or less in distance.

Accordingly, the floor construction 100 can advantageously reduce theoverall construction time of the construction project associated withthe floor construction 100, because the time delay in accessing thefloor underneath the floor construction 100 due to, for example, safetyand/or weather conditions, is substantially reduced or eliminated.Further, in a multi-level building construction having one or morefloors, the floor construction 100 can be placed above another floor.These floors are connected to and accessible via a construction elevator108. Accordingly, during the construction of the floor construction 100,the slab 104 area can be accessed via the elevator 108 because the gap106 has a distance that is small (or short) enough that the gap 106 canbe crossed over, and/or the gap 106 can be covered with small piece ofmaterial such as, for example, a sheet of metal or a plank of wood, toserve as a short bridge between the slabs 102, 104. Accordingly, theconstruction equipment can be easily moved between slab 104 and slab102. Thus, the generally required twenty to thirty day waiting periodfor accessing areas of the floor that cannot be reached due to theconventional gap (16 shown in FIG. 1) can be eliminated. In amulti-level building construction and/or very large buildingconstruction having large square footage floors, the reduction orelimination of the twenty to thirty day waiting period per gap compoundsto an enormous reduction in the overall construction time required forthe project.

Further, the gap 106 can substantially reduce or prevent weatherconditions to intrude into the floor beneath the floor construction 100.Thus, weather conditions no longer prevent work from being performed inthe floor underneath the floor construction 100. Therefore, waiting andtime delay associated with weather conditions can be reduced oreliminated from the construction process.

FIG. 6 shows a schematic side view of a floor construction 200 accordingto an embodiment. The floor construction 200 includes a floor 202 formedby joining two post-tensioned concrete slabs with a pour strip filledinto a gap between the two post-tensioned concrete slabs. The firstpost-tensioned concrete slab includes at least one rebar 204 that isconnected to a cavity-forming device 206. Preferably, the cavity-formingdevice 206 is less than a foot in length. The second post-tensionedconcrete slab includes another rebar 208 that is connected to thecavity-forming device 206. The rebars 204, 208 can be alignedsubstantially parallel with each other and/or aligned to be continuousalong the length (axial) direction. Although not shown in the schematicview, it will be understood that the floor construction 200 can includea plurality of rebars in the first post-tensioned concrete slab, whereineach of the rebars is fixed with respect to cavity-forming devices.Further, a plurality of rebars in the second post-tensioned concreteslab are each fixed with respect to the respective cavity-formingdevice, so that each cavity-forming device fixes the rebar of the firstpost-tensioned concrete slab with respect to the rebar of the secondpost-tensioned concrete slab. After a grout (a binding material) isinserted into the cavities of the cavity forming devices to fix therespective rebars in the cavities, the cavity-forming devices providestructural integrity to the floor and becomes the force and/or tensiontransferring devices. That is, force and/or tension can be transferredthrough the cavity-forming devices to and/or from the rebars.Preferably, the grout is stronger than the concrete slab.

FIG. 7 shows a schematic side view of an embodiment of a floorconstruction 300, which is similar to the floor construction 200 shownin FIG. 6. The floor construction 300 can include similar components asthe floor construction 200 of FIG. 6. The floor construction 300includes a floor 301 formed by joining two post-tensioned concrete slabswith a pour strip filled into a gap between the two post-tensionedconcrete slabs. The first post-tensioned concrete slab includes at leastone rebar 204 that is connected to a cavity-forming device 304 having acavity 306. The second post-tensioned concrete slab includes anotherrebar 208 that is inserted into the cavity 306 of the cavity-formingdevice 304. During the process of forming the floor construction 300,the end portion of the second rebar 208 is allowed to move within thecavity 306 of the cavity-forming device 304 during the tensioning of thesecond slab. After the second post-tensioned concrete slab is formed,the cavity 306 of the cavity-forming device 304 is filled with, forexample, grout material, to bind (e.g., fix and/or connect) the endportion of the second rebar 208 that is in the cavity 306 to thecavity-forming device 304. Accordingly, the cavity-forming device 304becomes connected to both the first rebar 204 and the second rebar 208.The rebars 204, 208 can be aligned substantially parallel with eachother and/or aligned to be continuous along the length (axial)direction. Although not shown in the schematic view, it will beunderstood that the floor construction 300 can include a plurality ofrebars in the first post-tensioned concrete slab, wherein each of therebars is connected to cavity-forming devices. Further, a plurality ofrebars in the second post-tensioned concrete slab are each connected tothe respective cavity-forming device, so that each cavity-forming devicefixes the rebar of the first post-tensioned concrete slab with respectto the rebar of the second post-tensioned concrete slab. The forceand/or tension can be transferred through the cavity-forming device 304to and/or from the rebars 204, 208.

FIG. 8 shows a schematic side view of an embodiment of a floorconstruction 310, which is similar to the floor construction 300 shownin FIG. 7. The floor construction 310 includes the first post-tensionedconcrete slab 312 and the second post-tensioned concrete slab 314, andthe pour strip 316 filled into the gap 318 that is between the twopost-tensioned concrete slabs 312, 314. The first post-tensionedconcrete slab 312 includes at least one rebar 204 that is connected to acavity-forming device 304 having a cavity 306. The cavity-forming device306 is positioned in the first post-tensioned concrete slab 312 so thatthe cavity 306 is provided as a part of the first post-tensionedconcrete slab 312. The end portion of the second rebar 208 is positionedin the cavity 306 of the cavity-forming device 304.

During the process of forming the floor construction 310, the endportion of the second rebar 208 is allowed to move within the cavity 306of the cavity-forming device 304 as the second post-tensioned concreteslab 314 is formed by tensioning of the concrete material. After thesecond post-tensioned concrete slab 314 is formed, the cavity 306 of thecavity-forming device 304 is filled with, for example, grout material tobind the end portion of the second rebar 208 that is in the cavity 306,and thus fixing the second rebar 208 with respect to the cavity-formingdevice 304.

FIG. 9 shows a schematic side view of an embodiment of a floorconstruction 320, which includes a first post-tensioned concrete slab322 and a second post-tensioned concrete slab 324, and a pour strip 326filled into a gap 328 that is between the two post-tensioned concreteslabs 322, 324. The first post-tensioned concrete slab 322 includes aplurality of rebars 326, 328 that are connected to respectivecavity-forming devices 330, 332, wherein each of the cavity-formingdevices 330, 332 has a cavity 334, 336. The cavity-forming devices 330,332 are positioned in the first post-tensioned concrete slab 322 so thatthe cavities 334, 336 are provided as parts of the first post-tensionedconcrete slab 322. End portions of a plurality of rebars 338, 340 of thesecond post-tensioned concrete slab 324 are positioned in the respectivecavities 334, 336. During the process of forming the floor construction320, the end portions of the rebars 338, 340 are allowed to move withinthe respective cavities 334, 336 as the second post-tensioned concreteslab 324 is formed by tensioning of the concrete material. After thesecond post-tensioned concrete slab 324 is formed, the cavities 334, 336are each filled with, for example, grout material to bind the endportions of the rebars 338, 340 to the respective cavity-forming devices330, 332.

FIGS. 10 and 11 show an embodiment of a floor construction 350. FIG. 10shows a schematic side view of the floor construction 350. FIG. 11 showsan enlarged schematic perspective view of the floor construction 350.The floor construction 350 includes a first post-tensioned concrete slab352 and a second post-tensioned concrete slab 354, and a pour strip 356filled into a gap 358 that is between the two post-tensioned concreteslabs 352, 354. FIG. 11 does not show the pour strip in the gap 358. Thefirst post-tensioned concrete slab 352 includes a plurality of rebars360, 362. The second post-tensioned concrete slab 354 includes aplurality of rebars 364, 366. At least one 362 of the rebars 360, 362 ofthe first post-tensioned concrete slab 352 is connected to acavity-forming device 368 having a cavity 370, wherein thecavity-forming device 368 is positioned at least partly within thematerial of the first post-tensioned concrete slab 352. Preferably, thecavity-forming device 368 is positioned completely within the materialof the first post-tensioned concrete slab 352. An end portion of therebar 366 of the second post-tensioned concrete slab 354 is positionedwithin the cavity 370. During the process of forming the floorconstruction 350, the end portion of the rebar 366 is allowed to movewithin the cavity 370 as the second post-tensioned concrete slab 354 isformed by tensioning of the concrete material. After the secondpost-tensioned concrete slab 354 is formed, the cavity 370 is filledwith, for example, grout material to bind the end portion of the rebar366 to the cavity-forming device 368. Further, at least one 364 of therebars 364, 366 of the second post-tensioned concrete slab 354 isconnected to a cavity-forming device 372 having a cavity 374, whereinthe cavity-forming device 372 is positioned at least partly within thematerial of the second post-tensioned concrete slab 354. Preferably, thecavity-forming device 372 is positioned completely within the materialof the second post-tensioned concrete slab 354. An end portion of one ofthe rebars 360 of the first post-tensioned concrete slab 352 ispositioned within the cavity 374. During the process of forming thefloor construction 350, the cavity-forming device 372 is allowed to moveas the second post-tensioned concrete slab 354 is formed by tensioningof the concrete material. Accordingly, while the end portion of therebar 360 is contained in the cavity 374, during the tensioning of theconcrete material in forming the second post-tensioned concrete slab354, the volume change of the concrete material moves the cavity-formingdevice 372 with respect to the rebar 360. After the secondpost-tensioned concrete slab 354 is formed, the cavity 374 is filledwith, for example, grout material to bind the end portion of the rebar360 to the cavity-forming device 372.

FIG. 12 shows a flow chart of an embodiment of a process 400 forconstructing the floor construction with reduced gap design. The processincludes a step 402 of positioning one or more rebars for a firstconcrete slab, prior to pouring the concrete material. Then, in step404, cavity-forming devices are positioned at near where an edge of theconcrete slab would form. Preferably, the cavity-forming devices aresplice devices connected to and/or positioned at ends of the rebars. Ifdesired, the cavity-forming devices can be connected, attached, and/orsecured on to the rebars of the first slab at this time. This particularstep can depend on the particular features of the cavity-forming deviceused. The process 400 includes a step 406 of forming the first concreteslab, wherein the first concrete slab includes one or more rebars andone or more cavities (and cavity-forming devices and/or splice devices).Preferably, the cavities are elongated and generally cylindrical inshape. Further, the cavities are positioned near the end of the firstconcrete slab. It is preferable that the cavities are formed by and/ordefined by one or more cavity-forming devices. It is preferable that theend portion and/or near the end of one or more rebars is connected to arespective cavity-forming device at or near an end portion of thecavity-forming device. It is possible that the end portion of one ormore rebars is positioned inside the cavity that is defined by thecavity-forming device, but not yet directly connected to thecavity-forming device. Further, it is possible that the ends of one ormore rebars are positioned to extend out from an edge of the first slab.It is preferable that these ends of the rebars do not extend more thansix inches beyond the edge of the first slab. It is more preferable thatthese ends of the rebars do not extend more than two inches beyond theedge of the first slab. It is even more preferable that the ends of therebars of the first concrete slab do not extend out from an edge of thefirst slab. The process 400 includes a step 408 of forming a firstpost-tensioned concrete slab by tensioning the concrete material of thefirst concrete slab. The process 400 further includes a step 410 ofpositioning the rebars for the second concrete slab so that their endsare positioned within respective cavities (e.g., inner chambers of thecavity-forming devices) of the first post-tensioned concrete slab. Thisstep 410 is performed prior to pouring the concrete for the secondconcrete slab. These rebars are positioned so that they can move withrespect to the cavities (e.g., cavity-forming devices, splice devices,and/or the edge of the first post-tensioned concrete slab). That is, forexample, the rebars for the second concrete slab are not secured to thecavity-forming devices at this stage of the process. It is preferablethat the positioning of the rebars for the second concrete slab withrespect to the cavity-forming devices are done after the first concreteslab has been tensioned (e.g., using the wire strand system that isincluded in the concrete slab) and has gone through the volume change,becoming the first post-tensioned concrete slab. Thus, the positioningof the rebars for the second concrete slab can be done with a desiredgap space in mind. That is, after the first post-tensioned concrete slabhas formed, the length change along the length direction of the rebarswould have been completed. Thus, the length of the gap can be estimatedand/or substantially determined. It is preferable that this estimatedand/or substantially determined gap distance is less than a foot. It iseven more preferable that this gap distance is less than six inches.Further, at this stage in the process 400, the cavities are open towhere the gap between the first and second concrete slabs will existwhen the second concrete slab is formed. The process 400 includes a step412 of pouring and forming the second concrete slab. The second concreteslab includes one or more rebars that have end portions positionedwithin the cavities of the first post-tensioned concrete slab and/or anyadditional cavity-forming devices that have been placed for formingadditional cavities within the second concrete slab. The process 400includes a step 414 of forming a second post-tensioned concrete slab bytensioning the concrete material of the second concrete slab. In step414, the second concrete slab is shortened along the length direction ofthe rebar by and due to tensioning of a wire strand system in the secondconcrete slab. Because the rebars for the second concrete slab are notsecured to the cavities of the first post-tensioned concrete slab, therebars can and do move with respect to the cavities during thetensioning of the second concrete slab. Likewise, if there are anyadditional cavity-forming devices that have been positioned to be withinthe second concrete slab, and these cavities contain ends of the rebarsof the first post-tensioned concrete slab, the additional cavities movewith respect to the rebars contained therein during the tensioning andforming the second post-tensioned concrete slab. After the volumechanges due to tensioning of the second concrete slab has beencompleted, the second concrete slab is the second post-tensionedconcrete slab. The process 400 includes a step 416 of connecting and/orsecuring the rebars of the second post-tensioned concrete slab to thecavity-forming devices. In addition, if in the step 404 thecavity-forming device was not secured to the rebar of the first concreteslab, then, in step 416, the cavity-forming device can be secured to thefirst rebar of the first post-tensioned concrete slab. Accordingly, inthe step 416, both of the first and second rebars of the first andsecond post-tensioned concrete slabs can be secured (e.g., fixed orconnected) within the cavity of the cavity-forming device (e.g., thisparticular step can depend on the particular features of thecavity-forming device used). At this stage in the process 400, the gapbetween the first post-tensioned concrete slab and the secondpost-tensioned concrete slab is generally fixed. Accordingly, the gapdistance is generally known. The gap distance of three feet or less ispossible. Preferably, the gap distance at this stage is one foot orless. Even more preferably, the gap distance is less than a foot. Theprocess 400 includes a step 418 of filling in the gap between the firstand second post-tensioned concrete slabs with material to form a pourstrip. When the pour strip is formed in the gap, the cavity-formingdevices connected to the rebars of the first and second post-tensionedconcrete slabs are covered by the pour strip. It is preferable that thecavity-forming devices positioned in the gap are completely covered bythe pour strip.

FIGS. 13-18 show schematic side views of floor constructions 500 a-f,respectfully, being constructed according to the process 400 describedabove and shown in FIG. 12. Like elements are referred to with the samereference numerals. The floor constructions 500 a-f show cavity-formingdevices 502, 504 having the same features. Each of the cavity-formingdevices 502, 504 has a generally cylindrical shape. In some embodiments,the cavity-forming device has an elongated shape with a geometric base(e.g., circle, oval, ovoid, triangle, square, rectangular, hexagon,octagon, etc.). The body 506 of the cavity-forming device 502 defines acavity 508, and the body 506 has an opening 510 at one of the ends thatallows access to the cavity by a rebar (530 shown in FIGS. 15-18). Thecavity 508 is configured to allow the rebar (530 shown in FIGS. 15-18)to move with respect to the cavity 508 and/or the splice device 502during tensioning of a concrete slab which includes the rebar (530 shownin FIGS. 15-18). The body 506 also has another end 512 opposite from theopening 510 along the length direction of the body 506. The end 512includes a connector 514 configured for connecting and securing to anend of a rebar 522. For example, the connector 514 can be a threadedchamber, wherein the inner side surface of the connector 514 is threadedto mate with matching threads of the rebar. Accordingly, the rebar 522that is used to connect at the end 512 of the cavity-forming device 502requires matching threads at the surface of the rebar 522. Thecavity-forming device 502 includes grout material for connecting therebars 522, 530. The cavity 508 can be accessed (e.g., for filling inthe cavity with the grout material in order to secure a portion of therebar to the cavity-forming device) via an inlet 516. The splice device502 can also include an outlet 518, wherein the air in the cavity 508can be evacuated out via the outlet 518 during the filling of the cavity508 with the grout material. Additionally and/or alternatively, the airin the cavity 508 can be evacuated out via the opening 510 during thefilling of the cavity 508 with the grout material. After the groutmaterial fills in the cavity 508, the rebars 522, 530 are connected orfixed securely via the cavity-forming device 502.

FIG. 13 shows the floor construction 500 a, wherein a first concreteslab 520 is formed with rebars 522, 524 therein (see steps 402 and 404in the process 400 of FIG. 12). End portions of the rebars 522, 524 areconnected to respective cavity-forming devices 502, 504. It is possiblethat the cavity-forming devices 502, 504 are positioned to not extendbeyond the end of the first concrete slab 520 and into a location 526where a gap will exist when a second concrete slab is formed.Optionally, the opening 510 can be covered with a sheath during thepouring of the concrete material when the first concrete slab 520 isbeing formed to prevent the concrete material from entering into thecavity 508. Further, the inlet 516 and the outlet 518 can have elongatedtubes to extend towards and out from the surface of the first concreteslab 520 to prevent the concrete material from entering into the cavity508.

FIG. 14 shows the floor construction 500 b, wherein the first concreteslab (520 shown in FIG. 13) has been tensioned and has become a firstpost-tensioned concrete slab 528. The volume of the first post-tensionedconcrete slab 528 has changed from the volume of the first concrete slab520, and a length of the first concrete slab 520 along the lengthdirection of the rebars 522, 524 has been reduced by the tensioning,indicated by ΔL₁ (see step 406 in the process 400 of FIG. 12).Accordingly, the first post-tensioned concrete slab 528 includescavities 508, 509 for receiving and containing ends of the rebars (530,532 shown in FIGS. 15-18) of the second concrete slab.

FIG. 15 shows the floor construction 500 c, wherein additional rebars530, 532 of the second concrete slab 534 are positioned so that each ofthe rebars 530, 532 has an end portion inside the respective cavities508, 509 of the first post-tensioned concrete slab 528 (see step 410 inthe process 400 of FIG. 12). The rebars 530, 532 can be aligned in alength direction of the rebars 522, 528 guided by the cavity-formingdevices 502, 504. The second concrete slab 534 is poured to include therebars 530, 532 (see step 412 in the process 400 of FIG. 12). Becausethe cavities 508, 509 in the first post-tensioned concrete slab 528accommodate the ends of the rebars 530, 532 and allow the rebars 530,532 to move during the tensioning of the second concrete slab 534, theedge of the second concrete slab 534 can be positioned closer to theedge of the first post-tensioned concrete slab 528 than conventionalfloor constructions. For example, it is possible that the distance fromthe edge of the second concrete slab 534 to the edge of the firstpost-tensioned concrete slab 528 is three feet or less. Preferably, thedistance from the edge of the second concrete slab 534 to the edge ofthe first post-tensioned concrete slab 528 is one foot or less.

FIG. 16 shows the floor construction 500 d, wherein the second concreteslab (534 shown in FIG. 15) has been tensioned and has become a secondpost-tensioned concrete slab 536 (see step 414 in the process 400 ofFIG. 12). Thus, the volume of the second post-tensioned concrete slab536 has changed from the volume of the second concrete slab 534, and alength of the second concrete slab 534 along the length direction of therebars 530, 532 has been reduced by the tensioning, indicated by ΔL₂.Where the gap 538 now exists, it is possible that the gap 538 is threefeet or less. Preferably, the gap 538 is one foot or less. Thecavity-forming devices 502, 504 are not yet secured to the rebars 530,532. Thus, during the change in volume and length of the second concreteslab, the rebars 530, 532 are allowed to move with respect to thecavities 508, 509 and/or the cavity-forming device 502, 504. Forexample, shown in FIG. 17, as the length of the second concrete slab isreduced in the floor construction 500 e, thus lengthening the locationbetween the first post-tensioned concrete slab 528 and the secondconcrete slab to form the gap 538, the rebars 530, 532 may move (e.g.,slide) away from the respective cavity-forming devices 502, 504 in thedirection of the length change indicated by ΔL₃. In embodiments, ΔL₂ isequal to, the same as, or substantially similar to ΔL₃. The lengthchange ΔL₃ does not move the end portion of the rebars 530, 532 so muchthat the length change ΔL₃ prevents the rebars 530, 532 from beingconnected and/or secured to the respective cavity-forming devices 502,504. This prevention is predetermined in the positioning of the rebars530, 532, for example, in step 410 in the process 400 of FIG. 12, and/orstructural features included in the cavity-forming devices 502, 504.After the volume change due to tensioning has been completed and thesecond post-tensioned concrete slab 536 has formed, the gap 538 betweenthe first post-tensioned concrete slab 528 and the second post-tensionedconcrete slab 536 is substantially defined.

FIG. 18 shows the floor construction 500 f, wherein the cavity-formingdevices 502, 504 have been securely connected to the end portions of therespective rebars 530, 532 (see step 416 in the process 400 of FIG. 12).The connection can be accomplished by filling the cavities 508, 509 ofeach of the cavity-forming devices 502, 504 with grout material forsecurely binding the end portions of the respective rebars 530, 532 tothe cavity-forming devices 502, 504. The floor construction 500 f ispositioned substantially horizontal with respect to the earth, and thefloor construction 500 f includes the first post-tensioned concrete slab528 and the second post-tensioned concrete slab 536 separated by the gap538. The cavity-forming devices 502, 504 are secured to the respectiverebars 522, 524, 530, 532 with sufficient strength for structuralapplicability for connecting the two post-tensioned concrete slabs 528,536 for structural purposes. The gap 538 has been filled in with amaterial to form a pour strip 540 (see step 418 in the process 400 ofFIG. 12). The pour strip 540 covers the gap 538 sufficiently forstructural purposes. Preferably, the gap 538 (e.g., edge to edge betweenthe slabs 528, 536) is completely covered by the pour strip 526.

FIG. 19 shows a schematic side view of an embodiment of a floorconstruction 600. The floor construction 600 can include similarcomponents as the floor construction 200 of FIG. 6 and/or the floorconstruction 300 of FIG. 7. The floor construction 600 includes a floor601 formed by joining two post-tensioned concrete slabs with a pourstrip filled into a gap between the two post-tensioned concrete slabs.The first post-tensioned concrete slab includes at least one rebar 204that is inserted into a cavity 602 of a cavity-forming device 604. Thesecond post-tensioned concrete slab includes another rebar 208 that isinserted into the cavity 602 of the cavity-forming device 604. Duringthe process of forming the floor construction 600, the end portion ofthe second rebar 208 is allowed to move within the cavity 602 during thetensioning of the second slab. After the second post-tensioned concreteslab is formed, the cavity 602 is filled with, for example, groutmaterial, to bind the end portions of the first and second rebars 204,208 that are in the cavity 602 of the cavity-forming device 604.Accordingly, the cavity-forming device 604 becomes fixed or connected toboth the first rebar 204 and the second rebar 208. The rebars 204, 208can be aligned substantially parallel with each other and/or aligned tobe continuous along the length (axial) direction. Although not shown inthe schematic view, it will be understood that the floor construction600 can include a plurality of rebars in the first post-tensionedconcrete slab, wherein each of the rebars is fixed with respect tocavity-forming devices. Further, a plurality of rebars in the secondpost-tensioned concrete slab are each fixed or connected with respect tothe respective cavity-forming device, so that each cavity-forming deviceconnects the rebar of the first post-tensioned concrete slab withrespect to the rebar of the second post-tensioned concrete slab.

FIG. 20 shows a schematic side view of an embodiment of a floorconstruction 610, which is similar to the floor construction 600 shownin FIG. 19. The floor construction 610 includes the first post-tensionedconcrete slab 612 and the second post-tensioned concrete slab 614, andthe pour strip 616 filled into the gap 618 that is between the twopost-tensioned concrete slabs 612, 614. The first post-tensionedconcrete slab 612 includes at least one cavity-forming device 620 havinga cavity 622. Accordingly, the cavity-forming device 620 forms thecavity 622 in the first post-tensioned concrete slab 612 having anopening 630 towards the gap 618. The end portions of the first andsecond rebars 204, 208 are positioned in the cavity 622. During theprocess of forming the floor construction 610, the end portion of thesecond rebar 208 is allowed to move within the cavity 622 as the secondpost-tensioned concrete slab 614 is formed by tensioning of the concretematerial. After the second post-tensioned concrete slab 614 is formed,the cavity 622 is filled with, for example, grout material 624, to bindthe end portions of the first and second rebars 204, 208 that are in thecavity 622 to the cavity-forming device 620. The cavity-forming device620 includes an inlet 626 for directing the grout material into thecavity 622, and an outlet 628 for directing flow of air and other fluidsand particles to aid in the grout material from entering and filling upthe cavity 622. Optionally, the cavity-forming device 620 may include alid at an opening 630 of the cavity for preventing cement material orother materials from entering into the cavity 622 when such preventionis needed and/or desired. For example, when pouring the concretematerials around the rebar 204, it may be desirable to prevent theconcrete materials from entering into the cavity 622. The lid can beplaced at the opening 630 to prevent the concrete materials fromentering into the cavity 622. Further, the inlet 626 and the outlet 628can be configured to have an elongated tube shape having a height thatis sufficient to extend to a top surface of the concrete slab 612. Theforce and/or tension in the floor construction 610 can be transferredthrough the cavity-forming device 620 to and/or from the rebars 204,208.

FIG. 21 shows a schematic side view of an embodiment of a floorconstruction 650, which is similar to the floor construction 600 shownin FIG. 19. The floor construction 650 includes the first post-tensionedconcrete slab 652 and the second post-tensioned concrete slab 654, andthe pour strip 616 filled into the gap 618 that is between the twopost-tensioned concrete slabs 652, 654. The second post-tensionedconcrete slab 654 includes at least one cavity-forming device 620 havinga cavity 622. Accordingly, the cavity-forming device 620 forms thecavity 622 in the second post-tensioned concrete slab 654 having anopening 630 towards the gap 618. The end portions of the first andsecond rebars 204, 208 are positioned in the cavity 622. During theprocess of forming the floor construction 610, the end portion of thesecond rebar 208 is allowed to move within the cavity 622 as the secondpost-tensioned concrete slab 614 is formed by tensioning of the concretematerial. After the second post-tensioned concrete slab 614 is formed,the cavity 622 is filled with, for example, grout material 624, to bindthe end portions of the first and second rebars 204, 208 that are in thecavity 622 to the cavity-forming device 620. The cavity-forming device620 includes an inlet 626 for directing the grout material into thecavity 622, and an outlet 628 for directing flow of air and other fluidsand particles to aid in the grout material from entering and filling upthe cavity 622. Optionally, the cavity-forming device 620 may include alid at an opening 630 of the cavity for preventing cement material orother materials from entering into the cavity 622 when such preventionis needed and/or desired. For example, when pouring the concretematerials around the rebar 208, it may be desirable to prevent theconcrete materials from entering into the cavity 622. The lid can beplaced at the opening 630 to prevent the concrete materials fromentering into the cavity 622. Further, the inlet 626 and the outlet 628can be configured to have an elongated tube shape having a height thatis sufficient to extend to a top surface of the concrete slab 654. Anembodiment of a floor construction includes both the configuration shownin FIGS. 20 and 21.

FIG. 22 shows a schematic side view of an embodiment of a floorconstruction 700. The floor construction 700 can include similarcomponents as the floor construction 200 of FIG. 6, the floorconstruction 300 of FIG. 7, and/or the floor construction 600 of FIG.19. The floor construction 700 includes a floor 701 formed by joiningtwo post-tensioned concrete slabs with a pour strip filled into a gapbetween the two post-tensioned concrete slabs. At least one of thepost-tensioned concrete slabs includes at least one rebar 708 that isinserted into a cavity 702 of a cavity-forming device 704. During theprocess of forming the floor construction 700, the end portion of therebar 708 is allowed to move within the cavity 702 during the tensioningof the associated concrete slab. After the post-tensioned concrete slabis formed, the cavity 702 is filled with, for example, grout material,to bind the end portions of the rebar 708 that is in the cavity 702 tothe cavity-forming device 704. Accordingly, the cavity-forming device704 becomes connected to the rebar 708. Although not shown in theschematic view, it will be understood that the floor construction 700can include a plurality of rebars in the first post-tensioned concreteslab, wherein each of the rebars can be connected to cavity-formingdevices. Further, a plurality of rebars in the second post-tensionedconcrete slab can be connected to the respective cavity-forming device.

FIG. 23 shows a schematic side view of an embodiment of a floorconstruction 710, which is similar to the floor construction 700 shownin FIG. 22. The floor construction 710 includes the first post-tensionedconcrete slab 712 and the second post-tensioned concrete slab 714, andthe pour strip 716 filled into the gap 718 that is between the twopost-tensioned concrete slabs 712, 714. The first post-tensionedconcrete slab 712 includes at least one cavity-forming device 720 havinga cavity 722. Accordingly, the cavity-forming device 720 forms thecavity 722 in the first post-tensioned concrete slab 712 having anopening 730 towards the gap 718. The cavity-forming device 720 caninclude a corrugated outer surface 740 that increases a surface area ofthe cavity-forming device 720. The increased surface area of the outersurface 740 can advantageously increase areas of contact between thecavity-forming device 720 and the concrete material of the concreteslab, and can enhance the structural strength in this region of thefloor construction. Further, the corrugated material making up thecavity-forming device 720 can be made from corrugated metal sheets,which can significantly reduce cost. The end portion of the rebar 708 ofthe second post-tensioned concrete slab 714 is positioned in the cavity722. During the process of forming the floor construction 710, the endportion of the rebar 708 is allowed to move within the cavity 722 as thesecond post-tensioned concrete slab 714 is formed by tensioning of theconcrete material. After the second post-tensioned concrete slab 714 isformed, the cavity 722 is filled with, for example, grout material 724,to bind the end portion of the rebar 708 in the cavity 722 to thecavity-forming device 720. The cavity-forming device 720 includes aninlet 726 for directing the grout material into the cavity 722, and anoutlet 728 for directing flow of air and other fluids and particles toaid in the grout material from entering and filling up the cavity 722.Optionally, the cavity-forming device 720 may include a lid at theopening 730 of the cavity 722 for preventing cement material or othermaterials from entering into the cavity 722 when such prevention isneeded and/or desired. For example, when pouring the concrete materialsaround the cavity-forming device 720, it may be desirable to prevent theconcrete materials from entering into the cavity 722. The lid can beplaced at the opening 730 to prevent the concrete materials fromentering into the cavity 722. Further, the inlet 726 and the outlet 728can be configured to have an elongated tube shape having a height thatis sufficient to extend to a top surface of the concrete slab 712.

FIG. 24 shows a schematic side view of an embodiment of a floorconstruction 750, which is similar to the floor construction 700 shownin FIG. 22. The floor construction 750 includes the first post-tensionedconcrete slab 752 and the second post-tensioned concrete slab 754, andthe pour strip 716 filled into the gap 718 that is between the twopost-tensioned concrete slabs 752, 754. The second post-tensionedconcrete slab 754 includes at least one cavity-forming device 720 havinga cavity 722. Accordingly, the cavity-forming device 720 forms thecavity 722 in the second post-tensioned concrete slab 754 having anopening 730 towards the gap 718. The end portion of the rebar 204 of thefirst post-tensioned concrete slab 752 is positioned in the cavity 722.During the process of forming the floor construction 710, thecavity-forming device 720 is allowed to move with respect to the endportion of the rebar 204 that is inside the cavity 722 as the secondpost-tensioned concrete slab 714 is formed by tensioning of the concretematerial. After the second post-tensioned concrete slab 714 is formed,the cavity 722 is filled with, for example, grout material 724, to bindthe end portion of the rebar 204 that is inside the cavity 722 of thecavity-forming device 720. The cavity-forming device 720 includes aninlet 726 for directing the grout material into the cavity 722, and anoutlet 728 for directing flow of air and other fluids and particles toaid in the grout material from entering and filling up the cavity 722.Optionally, the cavity-forming device 720 may include a lid at anopening 730 of the cavity for preventing cement material or othermaterials from entering into the cavity 722 when such prevention isneeded and/or desired. For example, when pouring the concrete materialsaround the cavity-forming device 720, it may be desirable to prevent theconcrete materials from entering into the cavity 722. The lid can beplaced at the opening 730 to prevent the concrete materials fromentering into the cavity 722. Further, the inlet 726 and the outlet 728can be configured to have an elongated tube shape having a height thatis sufficient to extend to a top surface of the concrete slab 754. Anembodiment of a floor construction includes both the configuration shownin FIGS. 23 and 24.

FIG. 25 shows a top-down plan view of an embodiment of the floorconstruction 800, wherein the floor construction 800 has all of thecavity-forming devices 802 in one of the first or second post-tensionedconcrete slabs 804, 805. The cavity-forming devices 802 can be the sameas the cavity-forming device (720 shown in FIGS. 23 and 24) describedabove. It is possible that the rebars 806 of one of the post-tensionedslabs are not directly connected to the cavity-forming devices 802.Nevertheless, the rebars 806 of one of the post-tensioned slabs arefixed in the slabs relative to the cavity-forming devices 802. Therebars 808 have end portions that are contained within the respectivecavities 810 of the cavity-forming devices 802.

FIG. 26 shows a top-down plan view of an embodiment of the floorconstruction 900, wherein the floor construction 900 has thecavity-forming devices 902 in both of the first or second post-tensionedconcrete slabs 904, 906. The cavity-forming devices 902 can be the sameas the cavity-forming device (720 shown in FIGS. 23 and 24) describedabove. It is possible that the rebars 908 of one of the post-tensionedslabs are not directly connected but are fixed in the slabs relative tothe cavity-forming devices 902. It is also possible that the rebars 908of one of the post-tensioned slabs 904 are connected to thecavity-forming devices 902. The rebars 910 have end portions that arecontained within the respective cavities 912 of the cavity-formingdevices 902.

Applications of the embodiments disclosed herein include all aspects ofconstruction, including, but not limited to, buildings, towers, floatingterminals, ocean structures and ships, storage tanks, nuclear containingvessels, bridge piers, bridge ducts, foundation soil anchorages, andvirtually all other types of installations where normally reinforcedconcrete may be acceptable.

Preferred embodiments have been described. Those skilled in the art willappreciate various modifications and substitutions are possible, withoutdeparting from the scope of the invention as claimed and disclosed,including the full scope of equivalents thereof.

What is claimed is:
 1. A concrete floor construction, comprising: afirst post-tensioned concrete floor slab, a second post-tensionedconcrete floor slab, and a cavity-forming device, said firstpost-tensioned concrete floor slab and said second post-tensionedconcrete floor slab having respective upper surfaces that are generallyaligned, said first post-tensioned concrete floor slab including aplurality of first rebars installed therein, said first post-tensionedconcrete slab being post-tensioned in at least a direction substantiallyparallel to said plurality of first rebars, said second post-tensionedconcrete floor slab including a plurality of second rebars installedtherein, said second post-tensioned concrete slab being post-tensionedin at least a direction substantially parallel to said plurality ofsecond rebars, said first post-tensioned concrete floor slab and saidsecond post-tensioned concrete floor slab being separated by a gap sothat the concrete material of said first post-tensioned concrete floorslab is not in contact with the concrete material of said secondpost-tensioned concrete floor slab, and said cavity-forming deviceforming a cavity, said cavity-forming device being installed in saidfirst post-tensioned concrete floor slab, wherein said cavity contains aportion of one of said second rebars.
 2. The concrete floor constructionaccording to claim 1, wherein said cavity-forming device has an endwhich is connected to an end portion of one of said first rebars,wherein said end has a threaded surface which mates with a threadedsurface of said end portion of the one of said first rebars.
 3. Theconcrete floor construction according to claim 1, wherein a portion ofone of said first rebars is also contained in said cavity.
 4. Theconcrete floor construction according to claim 3, wherein saidcavity-forming device has a pair of tubes extending upwardly throughsaid first post-tensioned concrete floor slab and providing air accessfrom above said post-tensioned concrete floor slab to said cavity, saidcavity being filled through one of said tubes with a binding materialwhich connects together said one of said first rebars and said one ofsaid second rebars so that the portion of said one of said first rebarsand the portion of said one of said second rebars are substantiallyparallel with each other.
 5. The concrete floor construction accordingto claim 3, wherein said cavity-forming device has a pair of tubesextending upwardly through said first post-tensioned concrete floor slaband providing air access from above said post-tensioned concrete floorslab to said cavity, said cavity being filled with a binding materialwhich connects together said one of said first rebars and said one ofsaid second rebars so that the portion of said one of said first rebarsand the portion of said one of said second rebars are substantiallyinline.
 6. The concrete floor construction according to claim 1, whereinsaid cavity-forming device has a pair of tubes extending upwardlythrough said first post-tensioned concrete floor slab and providing airaccess from above said post-tensioned concrete floor slab to saidcavity, said cavity being filled through one of said tubes with abinding material which fixes said one of said second rebars in saidcavity.
 7. The concrete floor construction according to claim 1, furthercomprising a second cavity foimed by a second cavity-forming deviceinstalled in said second post-tensioned concrete floor slab, whereinsaid second cavity contains a portion of one of said plurality of saidfirst rebars.
 8. The concrete floor construction according to claim 1,wherein said gap has a longer dimension for one side-to-side and ashorter dimension for another side-to-side, said shorter dimension beingthree feet or less and being shorter relative to said longer dimension.9. The concrete floor construction according to claim 1, wherein saidgap has a longer dimension for one side-to-side and a shorter dimensionfor another side-to-side, said shorter dimension being twelve (12)inches or less and being shorter relative to said longer dimension. 10.The concrete floor construction according to claim 1, furthercomprising: a strip of non-shrink material being in the gap, whereinsaid strip has a compressive strength that is greater than or equal to acompressive strength of the concrete material of said first and secondpost-tensioned concrete floor slabs.
 11. A concrete construction,comprising: a first post-tensioned concrete slab, a secondpost-tensioned concrete slab, and a cavity-forming device, said firstpost-tensioned concrete slab and said second post-tensioned concreteslab having respective upper surfaces that are generally aligned, saidfirst post-tensioned concrete slab including a plurality of first rebarsinstalled therein, said first post-tensioned concrete slab beingpost-tensioned in at least a direction substantially parallel to saidplurality of first rebars, said second post-tensioned concrete slabincluding a plurality of second rebars installed therein, said secondpost-tensioned concrete slab being post-tensioned in at least adirection substantially parallel to said plurality of second rebars,said first post-tensioned concrete slab and said second post-tensionedconcrete slab being separated by a gap so that the concrete material ofsaid first post-tensioned concrete slab is not in contact with theconcrete material of said second post-tensioned concrete slab, saidcavity-forming device forming a cavity, said cavity-forming device beinginstalled in said first post-tensioned concrete slab, wherein saidcavity contains a portion of one of said plurality of second rebars, andsaid cavity-forming device is not directly connected to said pluralityof first rebars.
 12. The concrete construction according to claim 11,wherein said one of said first rebars and the portion of said one ofsaid second rebars are substantially parallel with each other.
 13. Aconcrete floor construction, comprising: a first post-tensioned concretefloor slab, a second post-tensioned concrete floor slab, and acavity-forming device, said first post-tensioned concrete floor slab andsaid second post-tensioned concrete floor slab having respective uppersurfaces that are generally aligned, said first post-tensioned concretefloor slab including a plurality of first rebars installed therein, saidfirst post-tensioned concrete floor slab being post-tensioned in atleast a direction substantially parallel to said plurality of firstrebars, said second post-tensioned concrete floor slab including aplurality of second rebars installed therein, said second post-tensionedconcrete floor slab being post-tensioned in at least a directionsubstantially parallel to said plurality of second rebars, said firstpost-tensioned concrete floor slab and said second post-tensionedconcrete floor slab being separated by a gap so that the concretematerial of said first post-tensioned concrete floor slab is not incontact with the concrete material of said second post-tensionedconcrete floor slab, said cavity-forming device forming a cavity whichtogether with said device form a volume, said cavity-forming devicebeing installed in said first post-tensioned concrete floor slab,wherein one of said second rebars connects with said volume, said cavitybeing filled with a binding material which connects together said firstpost-tensioned concrete floor slab and said one of said second rebars,said gap having a longer dimension for one side-to-side and a shorterdimension for another side-to-side, said shorter dimension being twelve(12) inches or less and being shorter relative to said longer dimension,and said gap being filled with a strip of non-shrink material, whereinsaid strip has a compressive strength that is greater than or equal to acompressive strength of the concrete material of said first and secondpost-tensioned concrete floor slabs.
 14. A method for making a concretefloor construction including a first post-tensioned concrete floor slaband a second post-tensioned concrete floor slab separated by a gap,comprising: forming said first post-tensioned concrete floor slab with aplurality of first rebars, said first post-tensioned concrete floor slabbeing post-tensioned in at least a direction substantially parallel tosaid plurality of first rebars, wherein said first post-tensionedconcrete floor slab includes a cavity-forming device with a cavityhaving an opening towards an end of said first post-tensioned concretefloor slab; prior to pouring a second concrete floor slab, positioningone of a plurality of second rebars for said second concrete floor slabso that a portion of said one of said plurality of second rebars isinside said cavity; pouring said second concrete floor slab; forming thesecond post-tensioned concrete floor slab by tensioning said secondconcrete floor slab in at least a direction substantially parallel tosaid plurality of second rebars, thus forming said gap between saidfirst post-tensioned concrete floor slab and said second post-tensionedconcrete floor slab, wherein said gap has a longer dimension for oneside-to-side and a shorter dimension for another side-to-side, saidshorter dimension being shorter relative to said longer dimension; andafter forming said second post-tensioned concrete floor slab, securelyfixing said portion of said one of said plurality of said second rebarsin the cavity.
 15. The method according to claim 14, in said step ofsecurely fixing said portion of said second rebar in the cavity, alsosecurely fixing a portion of said first rebar in the cavity.
 16. Themethod according to claim 14, wherein said shorter dimension being threefeet or less in length.
 17. The method according to claim 14, furthercomprising: forming a strip of material in said gap with a non-shrinkmaterial, wherein said strip has a compressive strength that is greaterthan or equal to a compressive strength of the concrete material of saidfirst and second post-tensioned concrete floor slabs.
 18. A method formaking a concrete floor construction including a first post-tensionedconcrete floor slab and a second post-tensioned concrete floor slabseparated by a gap, comprising: forming said first post-tensionedconcrete floor slab, wherein said first post-tensioned concrete floorslab includes a first rebar installed therein, and an end portion ofsaid first rebar extends into a space that will become said gap, saidfirst post-tensioned concrete floor slab being post-tensioned in atleast a direction substantially parallel to said first rebar; before asecond post-tensioned concrete floor slab has been formed, positioning acavity-forming device having a cavity at an end portion of said firstrebar so that said end portion of said first rebar is inside saidcavity, but not securely connecting said cavity-forming device to saidend portion of said first rebar; pouring said second concrete floor slabsuch that the cavity forming device is positioned within an end of thesecond concrete floor slab; forming a second post-tensioned concretefloor slab by tensioning said second concrete floor slab in at least adirection substantially parallel to a second rebar installed within thesecond concrete floor slab, thus forming said gap between said firstpost-tensioned concrete floor slab and said second post-tensionedconcrete floor slab, wherein said gap has a longer dimension for oneside-to-side and a shorter dimension for another side-to-side, saidshorter dimension being shorter relative to said longer dimension; andafter forming said second post-tensioned concrete floor slab, securelyfixing said end portion of said first rebar in the cavity.
 19. Themethod according to claim 18, wherein prior to forming said secondpost-tensioned concrete floor slab, positioning the second rebar insidesaid cavity but not securely connecting said cavity-forming device tosaid second rebar; and in the securely fixing said portion of said firstrebar in the cavity step, also securely fixing a portion of the secondrebar of said second post-tensioned concrete floor slab in the cavity.20. The method according to claim 19, further comprising: forming astrip of material in said gap with a non-shrink material, wherein saidstrip has a compressive strength that is greater than or equal to acompressive strength of the concrete material of said first and secondpost-tensioned concrete floor slabs.